Legally Blonde
Fluffy and light, and has a pretty strong, inspirational core to it that advocates a golden mean between conformism and narcissism. Reese Witherspoon achieves self-realisation by helping others. And she can still wear pink if she wants. Win-win!
It’s not the most tightly-plotted, nor the most hilarious comedy ever made, though it does have some witty set-pieces, but as girls sleepover fare goes, probably essential.